The effects of bedroom air quality on sleep and next-day performance.

The effects of bedroom air quality on sleep and next-day performance were examined in two field-intervention experiments in single-occupancy student dormitory rooms. The occupants, half of them women, could adjust an electric heater to maintain thermal comfort but they experienced two bedroom ventilation conditions, each maintained for 1 week, in balanced order. In the initial pilot experiment (N = 14), bedroom ventilation was changed by opening a window (the resulting average CO2 level was 2585 or 660 ppm). In the second experiment (N = 16), an inaudible fan in the air intake vent was either disabled or operated whenever CO2 levels exceeded 900 ppm (the resulting average CO2 level was 2395 or 835 ppm). Bedroom air temperatures varied over a wide range but did not differ between ventilation conditions. Sleep was assessed from movement data recorded on wristwatch-type actigraphs and subjects reported their perceptions and their well-being each morning using online questionnaires. Two tests of next-day mental performance were applied. Objectively measured sleep quality and the perceived freshness of bedroom air improved significantly when the CO2 level was lower, as did next-day reported sleepiness and ability to concentrate and the subjects' performance of a test of logical thinking.

Effects of thermal discomfort in an office on perceived air quality, SBS symptoms, physiological responses, and human performance.

UNLABELLED: The effects of thermal discomfort on health and human performance were investigated in an office, in an attempt to elucidate the physiological mechanisms involved. Twelve subjects (six men and six women) performed neurobehavioral tests and tasks typical of office work while thermally neutral (at 22°C) and while warm (at 30°C). Multiple physiological measurements and subjective assessment were made. The results show that when the subjects felt warm, they assessed the air quality to be worse, reported increased intensity of many sick building syndrome symptoms, expressed more negative mood, and were less willing to exert effort. Task performance decreased when the subjects felt warm. Their heart rate, respiratory ventilation, and end-tidal partial pressure of carbon dioxide increased significantly, and their arterial oxygen saturation decreased. Tear film quality was found to be significantly reduced at the higher temperature when they felt warm. No effects were observed on salivary biomarkers (alpha-amylase and cortisol). The present results imply that the negative effects on health and performance that occur when people feel thermally warm at raised temperatures are caused by physiological mechanisms. PRACTICAL IMPLICATIONS: This study indicates to what extent elevated temperatures and thermal discomfort because of warmth result in negative effects on health and performance and shows that these could be caused by physiological responses to warmth, not by the distraction of subjective discomfort. This implies that they will occur independently of discomfort, i.e. even if subjects have become adaptively habituated to subjective discomfort. The findings make it possible to estimate the negative economic consequences of reducing energy use in buildings in cases where this results in elevated indoor temperatures. They show clearly that thermal discomfort because of raised temperatures should be avoided in workplaces.

Advantages for passengers and cabin crew of operating a gas-phase adsorption air purifier in 11-h simulated flights.

UNLABELLED: Experiments were carried out in a three-row, 21-seat section of a simulated aircraft cabin installed in a climate chamber to evaluate the extent to which passengers' perception of cabin air quality is affected by the operation of a gas-phase adsorption (GPA) purification unit. A total of 68 subjects, divided into four groups of 17 subjects took part in simulated 11-h flights. Each group experienced four conditions in balanced order, defined by two outside air supply rates (2.4 and 3.3 l/s per person), with and without the GPA purification unit installed in the recirculated air system, a total of 2992 subject-hours of exposure. During each flight the subjects completed questionnaires five times to provide subjective assessments of air quality, cabin environment, intensity of symptoms, and thermal comfort. Additionally, the subjects' visual acuity, finger temperature, skin dryness, and nasal peak flow were measured three times during each flight. Analysis of the subjective assessments showed that operating a GPA unit in the recirculated air provided consistent advantages with no apparent disadvantages. PRACTICAL IMPLICATIONS: Operating a gas-phase adsorption (GPA) air purifier unit in the recirculated air in a simulated airplane cabin provided a clear and consistent advantage for passengers and crew that became increasingly apparent at longer flight times. This finding indicates that the expense of undertaking duly blinded field trials on revenue flights would be justified.

Passenger evaluation of the optimum balance between fresh air supply and humidity from 7-h exposures in a simulated aircraft cabin.

UNLABELLED: A 21-seat section of an aircraft cabin with realistic pollution sources was built inside a climate chamber capable of providing fresh outside air at very low humidity. Maintaining a constant 200 l/s rate of total air supply, i.e. recirculated and make-up air, to the cabin, experiments simulating 7-h transatlantic flights were carried out at four rates of fresh outside air supply--1.4, 3.3, 4.7, and 9.4 l/s per person (3, 7, 10, and 20 cfm/person)--resulting in humidity levels, ranging from 7% to 28% relative humidity (RH). Four groups of 16-18 subjects acted as passengers and crew and were each exposed to the four simulated flight conditions. During each flight the subjects completed questionnaires three times to provide subjective ratings of air quality and of symptoms commonly experienced during flight. Physiological tests of eye, nose, and skin function were administered twice. Analysis of the subjective assessments showed that increasing RH in the aircraft cabin to 28% RH by reducing outside flow to 1.4 l/s per person did not reduce the intensity of the symptoms that are typical of the aircraft cabin environment. On the contrary, it intensified complaints of headache, dizziness, and claustrophobia, due to the increased level of contaminants. PRACTICAL IMPLICATIONS: The investigation shows that increasing aircraft cabin humidity by decreasing the ventilation flow rate of fresh outside air would not decrease reports of discomfort made by cabin occupants.

Impact of indoor air temperature and humidity in an office on perceived air quality, SBS symptoms and performance.

UNLABELLED: Perceived air quality (PAQ), sick building syndrome (SBS) symptoms and performance of office work were studied in a real office space at three levels of air temperature and humidity and two levels of ventilation rate (20 degrees C/40%, 23 degrees C/50%, 26 degrees C/60% RH at 10 l s(-1) p(-1) outside air, and 20 degrees C/40% RH at 3.5 l s(-1) p(-1) outside air). Thirty female subjects participated in the experiment. They were exposed to each environmental condition for 280 min. Thermal comfort was maintained at different thermal environments by self-adjustment of clothing. The subjects performed simulated office work throughout each exposure and repeatedly marked a set of visual-analog scales to indicate their perception of environmental conditions and of the intensity of SBS symptoms at the time. The study confirmed the previously observed impact of temperature and humidity on perceived air quality and the linear correlation between acceptability and enthalpy. The impact on perceived air quality of decreasing the ventilation rate from 10 to 3.5 l s(-1) per person could be counteracted by a decrement of temperature and humidity from 23 degrees C/50% RH to 20 degrees C/40% RH. Performance of office work was not significantly affected by indoor air temperature and humidity. However, several SBS symptoms were alleviated when the subjects worked at low levels of air temperature and humidity, which implies that a longer term exposure to low indoor air temperature and humidity might help to improve the performance of office work. PRACTICAL IMPLICATIONS: The findings of this study indicate the importance of indoor air temperature and humidity on perceived air quality and SBS symptoms. In practice, the required ventilation rate for comfort and health should no longer be independent of indoor air temperature and humidity.

The effects of indoor air quality on performance and productivity.

UNLABELLED: The main justification for ventilation has historically been to create a healthy indoor environment. Ventilation removes air pollutants originating inside the building, including bio-effluents. The outdoor air supply rate that has been found by experience to provide subjectively acceptable indoor air quality and to prevent the accumulation of moisture in the building is generally sufficient to maintain the concentration of pollutants at healthily low levels. Until 5 years ago this would have been the justification for current ventilation practices, but in 1999 the first of a series of experiments was published, revealing new mechanisms by which raised levels of indoor air pollution may reduce productivity, either in addition to or instead of having negative effects on comfort and health. It was shown in realistic experimental exposures lasting up to 5 h that the performance of simulated office work could be significantly increased by removing common indoor sources of air pollution, such as floor-coverings, used supply air filters and personal computers, or by keeping them in place and increasing the rate at which clean outdoor air was supplied from 3 to 10 to 30 l s(-1) per person. These short-term effects were demonstrated repeatedly even at pollutant levels that had no measurable effects on the perception of air quality by the occupants themselves, although there were effects on subclinical SBS symptoms such as headache. Temperature and noise distraction have since been studied in directly comparable exposures. The prediction arising from these experiments, that the performance of real office work over time would be significantly and substantially affected by the changes in indoor environmental quality that take place in the course of normal building operation, have recently been validated in 8-week field intervention experiments carried out in call-centers in northern Europe and the Tropics. These findings have far-reaching implications for the efficient use of energy in buildings. PRACTICAL IMPLICATIONS: It has now been shown beyond reasonable doubt that poor indoor air quality in buildings can decrease productivity in addition to causing visitors to express dissatisfaction. The size of the effect on most aspects of office work performance appears to be as high as 6-9%, the higher value being obtained in field validation studies. It is usually more energy-efficient to eliminate sources of pollution than to increase outdoor air supply rates. The experiments summarized in this article have documented and quantified relationships that can be used in making cost-benefit analyses of either solution for a given building. The high cost of labor per unit floor area ensures that payback times will usually be as low as 2 years.

Subjective perceptions, symptom intensity and performance: a comparison of two independent studies, both changing similarly the pollution load in an office.

The present paper shows that introducing or removing the same pollution source in an office in two independent investigations, one in Denmark and one in Sweden, using similar experimental methodology, resulted in similar and repeatable effects on subjective assessments of perceived air quality, intensity of sick building syndrome symptoms and performance of office work. Removing the pollution source improved the perceived air quality, decreased the perceived dryness of air and the severity of headaches, and increased typing performance. These effects were observed separately in each experiment and were all significant (P < or = 0.05) after combining the data from both studies, indicating the advantages of pollution source strength control for health, comfort, and productivity.

The effects of outdoor air supply rate in an office on perceived air quality, sick building syndrome (SBS) symptoms and productivity.

Perceived air quality, Sick Building Syndrome (SBS) symptoms and productivity were studied in a normally furnished office space (108 m3) ventilated with an outdoor airflow of 3, 10 or 30 L/s per person, corresponding to an air change rate of 0.6, 2 or 6 h-1. The temperature of 22 degrees C, the relative humidity of 40% and all other environmental parameters remained unchanged. Five groups of six female subjects were each exposed to the three ventilation rates, one group and one ventilation rate at a time. Each exposure lasted 4.6 h and took place in the afternoon. Subjects were unaware of the intervention and remained thermally neutral by adjusting their clothing. They assessed perceived air quality and SBS symptoms at intervals, and performed simulated normal office work. Increasing ventilation decreased the percentage of subjects dissatisfied with the air quality (P < 0.002) and the intensity of odour (P < 0.02), and increased the perceived freshness of air (P < 0.05). It also decreased the sensation of dryness of mouth and throat (P < 0.0006), eased difficulty in thinking clearly (P < 0.001) and made subjects feel generally better (P < 0.0001). The performance of four simulated office tasks improved monotonically with increasing ventilation rates, and the effect reached formal significance in the case of text-typing (P < 0.03). For each two-fold increase in ventilation rate, performance improved on average by 1.7%. This study shows the benefits for health, comfort and productivity of ventilation at rates well above the minimum levels prescribed in existing standards and guidelines. It confirms the results of a previous study in the same office when the indoor air quality was improved by decreasing the pollution load while the ventilation remained unchanged.

A study of local electrostatic filtration and main pre-filtration on airborne and surface dust levels in air-conditioned office premises.

The impact of electrostatic precipitation as a useful form of particulate filtration in the breathing zone is investigated in an intervention study in an air-conditioned commercial office in central London. Surface dust deposition and airborne dust levels are measured in the open plan zones of two floors--a control floor and a floor where the intervention is effected. The intervention consists of a sequence of weekly scenarios where the main pre-filters of the air-handling unit are switched between new and old filters, and where the electrostatic filters, located as uniformly as practicable on the open plan areas, are switched on or off. This 2 x 2 set of interventions is repeated over 4 cycles. It was found that the breathing zone filtration (BZF) by electrostatic precipitators reduces airborne dust significantly and appears to be more efficient in reducing smaller sized particles. No significant effect of BZF filters in reducing surface dust deposition was detected.

Visual analogue scales for detecting changes in symptoms of the sick building syndrome in an intervention study.

OBJECTIVES: This study tested questionnaires using visual analogue scales (VAS) in a cleaning intervention study and attempted to find a simple way of analyzing the replies to the questionnaires. METHODS: A VAS questionnaire made up of 26 questions was developed and marked once a week for 28 weeks by the room occupants in 3 buildings. A total of 1248 questionnaires was used in the analysis of the results. A simple model based on the differences between a person's average responses during 2 different periods was used in the analysis. RESULTS: No clear effect of the cleaning was found. Several significant correlations between different questions were established. Estimates for the design of future studies are given. CONCLUSIONS: The VAS questionnaire proved to be feasible for this type of study. It is suggested that each intervention period should last 4 weeks if the questionnaire is used once a week. However, the length of the period also depends on the expected latency of the symptoms, on how long it takes for environmental conditions to be affected by the intervention, and on how quickly conditions return to "normal" during control periods.

Perceived air quality, sick building syndrome (SBS) symptoms and productivity in an office with two different pollution loads.

Perceived air quality, Sick Building Syndrome (SBS) symptoms and productivity were studied in an existing office in which the air pollution level could be modified by introducing or removing a pollution source. This reversible intervention allowed the space to be classified as either non-low-polluting or low-polluting, as specified in the new European design criteria for the indoor environment CEN CR 1752 (1998). The pollution source was a 20-year-old used carpet which was introduced on a rack behind a screen so that it was invisible to the occupants. Five groups of six female subjects each were exposed to the conditions in the office twice, once with the pollution source present and once with the pollution source absent, each exposure being 265 min in the afternoon, one group at a time. They assessed the perceived air quality and SBS symptoms while performing simulated office work. The subject-rated acceptability of the perceived air quality in the office corresponded to 22% dissatisfied when the pollution source was present, and to 15% dissatisfied when the pollution source was absent. In the former condition there was a significantly increased prevalence of headaches (P = 0.04) and significantly lower levels of reported effort (p = 0.02) during the text typing and calculation tasks, both of which required a sustained level of concentration. In the text typing task, subjects worked significantly more slowly when the pollution source was present in the office (P = 0.003), typing 6.5% less text than when the pollution source was absent from the office Reducing the pollution load on indoor air proved to be an effective means of improving the comfort, health and productivity of building occupants.

Ventilation efficiencies of desk-mounted task/ambient conditioning systems.

In laboratory experiments, we investigated two task/ambient conditioning systems with air supplied from desk-mounted air outlets to efficiently ventilate the breathing zone of heated manikins seated at desks. In most experiments, the task conditioning systems provided outside air while a conventional ventilation system provided additional space cooling but no outside air. Air change effectiveness (i.e., exhaust air age divided by age of air at the manikin's face) was measured with a tracer gas step-up procedure. Other tracer gases simulated the release of pollutants from nearby occupants and from the floor covering, and the associated pollutant removal efficiencies (i.e., exhaust air concentrations divided by concentrations at manikin's face) were calculated. High values of air change effectiveness (approximately 1.3 to 1.9) and high values of pollutant removal efficiency (approximately 1.2 to 1.6) were measured when these task conditioning systems supplied 100% outdoor air at a flow rate of 7 to 9 L s-1 per occupant. Air change effectiveness was reasonably well correlated with the pollutant removal efficiency. Overall, the experimental data suggest that these task/ambient conditioning systems can be used to improve ventilation and air quality or to save energy while maintaining a typical level of IAQ at the breathing zone.

An experimental study of the effects of energy intake at breakfast on the test performance of 10-year-old children in school.

In order to examine the effect of energy intake at breakfast on school performance the same morning, the parents of ten parallel school classes of 10-year-old school children at five different schools were persuaded to alter their child's breakfast regimen at home over a period of 4 successive days. A total of 195 families were provided with standard breakfasts with either low or high energy content. Uneaten food was returned and weighed. Individual children were randomly assigned to breakfast alternative on any given day. The teachers who carried out the performance assessments at school were blind to treatment condition. Voluntary physical endurance and the performance of a creativity test were significantly better after a breakfast from which children derived over 20% of their recommended daily energy intake than after a breakfast from which they obtained less than 10% of recommended values. The error rate in an addition task was negatively correlated and the rate of working in a number checking task was positively correlated with individual energy intake from the low-energy breakfast. Significantly fewer children reported feeling bad and self-estimates of hunger sensation were lower during the morning at school after the high energy breakfast. Estimates of energy intake at breakfast based on 24-h dietary recall interviews with the children carried out by telephone at their homes showed good correlation with estimates based on returned food (r = 0.89). Energy intake at breakfast as estimated from returned food had no significant effect on energy intake at school lunch as estimated by dietary recall.

Effects of moderate heat stress on driver vigilance in a moving vehicle.

A total of 83 drivers, 51 males and 32 females, aged 25-65, were recruited to drive an apparently unmodified passenger car for 1 h over at least four laps of a predetermined route on public roads, which included seven sets of traffic lights and sections limited to 50, 70, 90 and 110 km/h. They were randomly assigned to one of two thermal conditions (21 or 27 degrees C), and drove only during the hours of daylight. A computer initiated unprepared signals to which drivers would normally be alert. Drivers responded by pressing a foot-switch and reporting verbally. Signals were selected at random from 21 possible signals, and were presented for up to 3 min, with a random delay of 30-180 s after each response or failure to respond. The negative effect of heat stress on vigilance was statistically significant. At 27 degrees C, the overall proportion of missed signals was 50% higher and response times were 22% longer than they were at 21 degrees C. These effects of heat were significant and proportionally greater in the second half-hour, for subjects < 40 years and for speeds below 60 km/h (i.e. in city traffic). The latter finding suggests that heat may have increased arousal, and there was some indication of a redistribution of attention away from the most peripheral signals at the higher temperature. Overt driving errors were observed significantly more often at 27 degrees C than at 21 degrees C for women only.

Wind-chill equations predicting whole-body heat loss for a range of typical civilian outdoor clothing ensembles.

A thermal manikin with constant skin temperature and a wind-chill tunnel with constant air temperatures and wind speeds were used to measure whole-body heat loss for seven ensembles chosen to represent the full range of civilian outdoor clothing in use for everyday, nonsporting wear. Equations fitting the data with correlation coefficients exceeding 0.99 were derived for each ensemble, and diagrams were produced with these equations to interpolate and extend the range of conditions. The conditions studied were those resulting in total heat loss from 50 to 250 W.m-2, so very little extrapolation was required. The wind-chill equivalent temperature (with reference to 2 m.s-1), based on the average value for all seven ensembles, showed good agreement on this measure. The values predicted on the basis of whole-body heat loss through clothing were shown to be much lower than those predicted from the Siple wind-chill index for unprotected skin.

Use of thermal manikins in environmental ergonomics.

Thermal manikins are a fairly standard tool in environmental ergonomics. As they can provide a rapid, accurate, and reproducible simulation of the physical processes of dry heat loss to the environment, their main application is in the study of neutral or cold conditions at relatively low activity levels. Thermal manikins provide a good estimate of the total dry heat loss from the body and the distribution of heat flow over the body surface. In a standard environment, these measures can be used to describe the thermal characteristics of clothing. With standard clothing, complex thermal environments, eg, as in vehicles, can also be quantitatively compared and evaluated. Future developments include improved simulation of evaporative heat loss; improved software for simulating internal heat transfer, heat storage, and vasoconstriction; reactive programs with target total heat loss; empirical equations predicting manikin response to temperature, air velocity, etc; and standard techniques for testing diving and survival suits.

Measurement of acute response to draught in the eye.

In order to assess the sensitivity to draught of 7 different tests, 41 volunteer subjects were exposed experimentally: 18 to 1.0 m/s and 9 to 0.5 m/s in a climate chamber: 14 to an average of 0.67 m/s in an air-conditioned car. All exposures were at 21-22 degrees C. Exposures were for 30 min indoors, 45 min in the car. Break-up Time (BUT) of the pre-corneal film after a blink was observed before and after exposure in the laboratory. There was a significant decrease after exposure to 1.0 m/s (P less than 0.01) but not to 0.5 m/s. The variance of the observed BUT increased after exposure to 0.5 m/s (P less than 0.05). The Norn Lacrimal Dilution test showed increased tear flow after the climate-chamber exposures (P less than 0.05). Self-reported BUT(S) was always several times longer than BUT. There was a significant correlation between these measures (P less than 0.05) before exposure, but not after. BUT(S), like BUT, decreased after exposure to 1.0 m/s (P less than 0.01), but not after 0.05 m/s. However, the variance of BUT(S) did not increase significantly after 0.5 m/s; it decreased significantly after 1.0 m/s (P less than 0.01). A significantly improved mucus ferning pattern was observed after draught exposure (P less than 0.005), presumably due in part to increased lacrimal flow. There was no significant effect of draught on the albumin content of tear samples taken before and after exposure. Lissamine Green staining performed before and after exposure revealed no effect on micro-damage to the conjunctival epithelium.

Response of solvent-exposed printers and unexposed controls to six-hour toluene exposure.

The acute effects of toluene were studied in 43 male printers and 43 control subjects matched according to sex, age, educational level, and smoking habits. The mean age of the subjects was 36 (range 29-50) years. The printers had been exposed to solvents for 9 to 25 years during employment at flexo and rotogravure printing plants, while the controls had no history of solvent exposure. Each subject was exposed once in a climate chamber to either 100 ppm of toluene or clean air for 6.5 h preceded by a 1-h acclimatization period. The effects of toluene were measured from subjective votes with linear analogue rating scales on 16 items, and on the performance of 10 different tests measuring psychomotor skills, perceptual skills, and vigilance. Exposure to 100 ppm of toluene compared with exposure to clean air caused discomfort with complaints of low air quality, strong odor, fatigue, sleepiness, a feeling of intoxication, and irritation of the eyes, nose and throat. Furthermore, the subjects exposed to toluene showed decreased manual dexterity, decreased color discrimination, and decreased accuracy in visual perception. There was no significant difference in the effects of toluene on printers compared to those of toluene on controls, but tendencies toward a greater sensitivity were seen for the printers in two tests.